Sewing machine



FIG. 1 is a front and side perspective view of our design for a sewing machine;

FIG. 2 is a side view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is an opposite side view thereof;

FIG. 5 is a rear view thereof; and,

FIG. 6 is a top view thereof.

The areas shown in broken lines show environmental structure and form no part of the claimed design. The bottom view is not shown and forms no part of the claimed design. 

The ornamental design for a sewing machine, as shown and described. 